Text messaging, or texting, is the act of composing and sending brief, electronic messages between two or more mobile phones, or fixed or portable devices over a phone network. The term originally referred to messages sent using the Short Message Service (SMS). However, text messaging has grown to include messages containing image, video, and sound content (known as Multi Media Message Service (MMS) messages). The sender of a text message is known as a texter, while the service itself has different colloquialisms depending on the region.
Enhanced Messaging Service (EMS) is a cross-industry collaboration between manufactures of wireless mobile devices and the carriers of wireless subscriber networks. EMS is an application-level extension to the SMS format for wireless phones available on Global System for Mobile Communications (GSM) networks, code division multiple access (CDMA) networks and other networks (e.g. the Internet).
A User Data Header (UDH) is a binary structure which may be present at the start of a short message (e.g., a text message and/or a message with a digital photograph) segment in the Short Message Service (SMS) in a GSM format and/or a CDMA format. A UDH does not contain text of the short message, and the UDH specifies how the short message should be formatted and processed. Additionally, user data in the short message segment can include the text and/or the coding of a picture (e.g., a digital photograph) for the message.